http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/stomach/vomiting.h tml There is also considerable variability among species in the propensity for vomition. Rats reportedly do not vomit. Cattle and horses vomit rarely - this is usually an ominous sign and most frequently a result of acute gastric distension. Carnivores such as dogs and cats vomit frequently, often in response to such trivial stimuli as finding themselves on a clean carpet. Humans fall between these extremes, and interestingly, rare individuals have been identified that seem to be incapable of vomiting due to congenital abnormalities in the vomition centers of the brainstem.